In the evolution from reptiles to mammals, the development of audiovocal communication became of utmost importance in maintaining maternal-offspring contact, as well as contact of members of social groups. The isolation call (separation call) is perhaps the most primitive and basic of mammalian vocalizations. In preceding work on squirrel monkeys (Z01 MH 00787-01 LBEB) it was shown that tegmental lesions involving the gray matter at the junction of the third ventricle and aqueduct affects the patterning and production of the isolation call. Since the rostral limbic cortex is the main cortical region involved in the vocalization of monkeys and since it projects to the core gray matter in question, the present project is designed to assess the effects of ablating this cortical region on the production and regulation of the isolation call. In addition to te initial results of these experiments, the present report describes the findings in a subsidiary study concerned with the effects of opiate drugs on the production of isolation calls.